Date of Award

Spring 2022

Document Type

Open Access Dissertation

Department

Biological Sciences

First Advisor

Jeffry L. Dudycha

Abstract

Resource variability and availability often drives competition within ecosystems, which can lead to the diversification of organismal niches and physiological capabilities. In aquatic systems, common resources that photosynthetic organisms, such as algae, compete for are light and carbon. Both the spectral characteristics (color) and carbon concentrations of an aquatic system vary with time and space, which means that algae need to be able to respond to changes in resource availability to survive. Using a group of ubiquitous unicellular eukaryotes known as cryptophytes, we investigated both how cryptophytes respond to changes in the available light spectrum at a physiological and genetic level, and how they respond to changes in light and carbon availability.

First, we grew cryptophytes with different pigment complements (three phycoerythrin-containing and one phycocyanin-containing) under wide-spectrum, red, green, and blue light. We examined how these cryptophytes responded to changes in available light color, expecting that they would shift pigment physiology to maximize light capture as predicted by the theory of chromatic acclimation, and that gene expression would mirror any shifts in physiology. We found that pigment complement seems to be related to how cryptophytes respond to available spectra, and that light acclimation strategies related to habitat history may explain unexpected results observed in some species. Additionally, we found that post-transcriptional modification seems to play a role in genetic regulation of our physiological observations.

Second, we grew cryptophytes of varying sizes in habitats with varying light availability and carbon sources to examine the plasticity by which cryptophytes respond to changes in potential food supply. We expected that size would be a driver for carbon acquisition, and that cryptophytes would be able to survive in the darkness with added carbon to supplement photosynthetic losses. We found that growth, volume, and pigment concentrations all varied with species and treatment. Four species exhibited heterotrophy using glucose as a carbon source, and no cryptophytes were able to survive on bacteria in the dark. Both bacteria and glucose affected how cryptophytes grew in the light, but this varied with species. Overall, our results suggest that resource acquisition strategies are highly plastic in cryptophytes.

Rights

© 2022, Rachel Ann-Marie Schomaker

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